1. Field of the Invention
The present invention generally relates to apparatus for controlling a tape tension and, more particularly, is directed to an apparatus having a vacuum chamber for controlling a tape tension in which a slackened portion of a tape is introduced into a vacuum chamber and the tape is absorbed by a negative pressure within the vacuum chamber, thereby the tape being applied with a tension.
2. Description of the Prior Art
Conventionally, when a tape cassette is manufactured, a cassette casing and a magnetic tape are prepared independently and the magnetic tape is wound around a reel provided within the cassette casing by an apparatus described, for example, in Japanese Laid-Open Patent Gazette No. 63-300475. To be more concrete, a leader tape fixed to the reel within the cassette casing is cut and the magnetic tape is connected to an end portion of the thus cut leader tape. Then, the magnetic tape is wound around the reel by a predetermined amount by rotating the reel. After the magnetic tape is wound around the reel, the rear end of the magnetic tape is cut and connected to a free end of the leader tape connected to an opposite reel, thereby being wound within the tape cassette.
When the magnetic tape is wound within the tape cassette as set forth above, a tape tension of the magnetic tape must be kept at substantially a constant value. To this end, a tension arm is provided in the tape running path of the magnetic tape and the tension arm is rotated in response to the change of the magnetic tape so as to adjust the tape tension.
In such tape winding apparatus, the control operation for controlling a tape tension by the tension arm has a problem of a responsive characteristic. That is, if the magnetic tape is wound at high speed in order to increase productivity in winding the magnetic tape within the tape cassette, there is then the disadvantage that the tension arm cannot follow the change of the tape tension. Accordingly, the conventional tape winding apparatus utilizing the tension arm has a shortcoming that the tape winding speed is limited.
In order to remove the aforenoted disadvantages, it is proposed to wind the magnetic tape around the reels while a tension is applied to the magnetic tape by a vacuum chamber. However, the vacuum chamber is used to perform a constant tape tension control so that, when the tape tension is changed by the vacuum chamber, the pressure of the vacuum source must be changed. There is then the disadvantage that the change of tape tension during the winding process of the magnetic tape cannot be controlled.